1. Failure of either one of two related phenomena to keep pace with the other; or any situation in which the value of one depends on whether the other has been increasing or decreasing. 2. The lag of a magnetic effect behind its cause. 3. The temperature differential that exists when a substance, such as reversible hydrocolloid, melts at one temperature and solidifies at another. 4. The basis of a type of cooperativity observed in many enzyme-catalyzed reactions in which the degree of cooperativity is associated with a slow conformational change of the enzyme. 5. The nonlinear nature of the pressure-volume curve of the lung in which transpulmonary pressure at a given volume during inflation is less than the transpulmonary pressure at the same volume during exhalation.